Breast cancer stem cells generate immune-suppressive T regulatory cells by secreting TGFß to evade immune-elimination.

Cancer stem cells (CSCs), being the primary contributors in tumor initiation, metastasis, and relapse, ought to have seminal roles in evasion of immune surveillance. Tumor-promoting CD4+CD25+FOXP3+ T-regulatory cells (Tregs) have been described to abolish host defense mechanisms by impeding the activities of other immune cells including effector T cells. However, whether CSCs can convert effector T cells to immune-suppressive Treg subset, and if yes, the mechanism underlying CSC-induced Treg generation, are limitedly studied. In this regard, we observed a positive correlation between breast CSC and Treg signature markers in both in-silico and immunohistochemical analyses. Mirroring the conditions during tumor initiation, low number of CSCs could successfully generate CD4+CD25+FOXP3+ Treg cells from infiltrating CD4+ T lymphocytes in a contact-independent manner. Suppressing the proliferation potential as well as IFNγ production capacity of effector T cells, these Treg cells might be inhibiting antitumor immunity, thereby hindering immune-elimination of CSCs during tumor initiation. Furthermore, unlike non-stem cancer cells (NSCCs), CSCs escaped doxorubicin-induced apoptosis, thus constituting major surviving population after three rounds of chemotherapy. These drug-survived CSCs were also able to generate CD4+CD25+FOXP3+ Treg cells. Our search for the underlying mechanism further unveiled the role of CSC-shed immune-suppressive cytokine TGFß, which was further increased by chemotherapy, in generating tumor Treg cells. In conclusion, during initiation as well as after chemotherapy, when NSCCs are not present in the tumor microenvironment, CSCs, albeit present in low numbers, generate immunosuppressive CD4+CD25+FOXP3+ Treg cells in a contact-independent manner by shedding high levels of immune-suppressive Treg-polarizing cytokine TGFß, thus escaping immune-elimination and initiating the tumor or causing tumor relapse.

Tumor-Associated CD19+CD39- B Regulatory Cells Deregulate Class-Switch Recombination to Suppress Antibody Responses.

B cells are an essential component of humoral immunity. Their primary function is to mount antigen-specific antibody responses to eliminate pathogens. Despite an increase in B-cell number, we found that serum-IgG levels were low in patients with breast cancer. To solve this conundrum, we used high-dimensional flow cytometry to analyze the heterogeneity of B-cell populations and identified a tumor-specific CD19+CD24hiCD38hi IL10-producing B regulatory (Breg)-cell subset. Although IL10 is a Breg-cell marker, being an intracellular protein, it is of limited value for Breg-cell isolation. Highly expressed Breg-cell surface proteins CD24 and CD38 also impede the isolation of viable Breg cells. These are hurdles that limit understanding of Breg-cell functions. Our transcriptomic analysis identified, CD39-negativity as an exclusive, sorting-friendly surface marker for tumor-associated Breg cells. We found that the identified CD19+CD39‒IL10+ B-cell population was suppressive in nature as it limited T helper-cell proliferation, type-1 cytokine production, and T effector-cell survival, and augmented CD4+FOXP3+ regulatory T-cell generation. These tumor-associated Breg cells were also found to restrict autologous T follicular helper-cell expansion and IL21 secretion, thereby inhibiting germinal transcript formation and activation-induced cytidine deaminase expression involved in H-chain class-switch recombination (CSR). This isotype-switching abnormality was shown to hinder B-cell differentiation into class-switched memory B cells and subsequent high-affinity antibody-producing plasma B cells, which collectively led to the dampening of IgG-mediated antibody responses in patients with cancer. As low IgG is associated with poor prognosis in patients with cancer, Breg-cell depletion could be a promising future therapy for boosting plasma B cell-mediated antibody responses.

FOXP3/HAT1 Axis Controls Treg Infiltration in the Tumor Microenvironment by Inducing CCR4 Expression in Breast Cancer.

Infiltrating T-regulatory cells in the tumor microenvironment is a key impediment to immunotherapy and is linked to a poor prognosis. We found that tumor-infiltrating Tregs express a higher expression of the chemokine receptor CCR4 than peripheral Tregs in breast cancer patients. CCL22 and CCL17 are released by tumor cells and tumor-associated macrophages, attracting CCR4+ Tregs to the tumor site. The Treg lineage-specific transcription factor FOXP3 changes the CCR4 promoter epigenetically in conjunction with HAT1 to provide a space for FOXP3 binding and activation of the CCR4 gene. To increase CCR4 expression in Tregs, the FOXP3/HAT1 axis is required for permissive (K23 and K27) or repressive (K14 and K18) acetylation of histone-3. In murine breast and melanoma tumor models, genetic ablation of FOXP3 reduced CCR4+ Treg infiltration and tumor size while also restoring anti-tumor immunity. Overexpression of FOXP3, on the other hand, increased CCR4+ Treg infiltration, resulting in a decreased anti-tumor immune response and tumor progression. These findings point to FOXP3 playing a new role in the tumor microenvironment as a transcriptional activator of CCR4 and a regulator of Treg infiltration.

The Adroitness of Andrographolide as a Natural Weapon Against Colorectal Cancer.

The conventional carcinoma treatment generally encompasses the employment of radiotherapy, chemotherapy, surgery or use of cytotoxic drugs. However, recent advances in pharmacological research have divulged the importance of traditional treatments in cancer. The aim of the present review is to provide an overview of the importance of one such medicinal herb of Chinese and Indian origin: Andrographis paniculate on colorectal cancer with special emphasis on its principal bioactive component andrographolide (AGP) and its underlying mechanisms of action. AGP has long been known to possess medicinal properties. Studies led by numerous groups of researchers shed light on its molecular mechanism of action. AGP has been shown to act in a multi-faceted manner in context of colorectal cancer by targeting matrix metalloproteinase-9, Toll-like receptor or NFκB signaling pathways. In this review, we highlighted the recent studies that show that AGP can act as an effective immunomodulator by harnessing effective anti-tumor immune response. Recent studies strongly recommend further research on this compound and its analogues, especially under in-vivo condition to assess its actual potential as a prospective and efficient candidate against colorectal cancer. The current review deals with the roles of this phytomedicine in context of colorectal cancer and briefly describes its perspectives to emerge as an essential anti-cancer drug candidate. Finally, we also point out the drawbacks and difficulties in administration of AGP and indicate the use of nano-formulations of this phytomedicine for better therapeutic efficacy.

GFI1/HDAC1-axis differentially regulates immunosuppressive CD73 in human tumor-associated FOXP3+ Th17 and inflammation-linked Th17 cells.

Plasticity between Th17 and Treg cells is regarded as a crucial determinant of tumor-associated immunosuppression. Classically Th17 cells mediate inflammatory responses through production of cytokine IL17. Recently, Th17 cells have also been shown to acquire suppressive phenotypes in tumor microenvironment. However, the mechanism by which they acquire such immunosuppressive properties is still elusive. Here, we report that in tumor microenvironment Th17 cell acquires immunosuppressive properties by expressing Treg lineage-specific transcription factor FOXP3 and ectonucleotidase CD73. We designate this cell as Th17reg cell and perceive that such immunosuppressive property is dependent on CD73. It was observed that in classical Th17 cell, GFI1 recruits HDAC1 to change the euchromatin into tightly-packed heterochromatin at the proximal-promoter region of CD73 to repress its expression. Whereas in Th17reg cells GFI1 cannot get access to CD73-promoter due to heterochromatin state at its binding site and, thus, cannot recruit HDAC1, failing to suppress the expression of CD73.

Transcriptional regulation of VEGFA expression in T-regulatory cells from breast cancer patients.

The initiation of new blood vessel formation (neo-angiogenesis) is one of the primary requirements for the establishment of tumor. As the tumor grows beyond a certain size, a hypoxic-condition arises in the inner core of tumor, triggering the release of chemokines, which attract T-regulatory (Treg) cells in the tumor-site. The presence of FOXP3, a lineage-specific transcription factor, expressing Treg cells in various types of tumor implements immunosuppressive and tumor-promoting strategies. One such strategy is the invitation of endothelial cells for neo-vascularization in the tumor site. Here we report that as the disease progresses, Treg cells from breast cancer patients are capable of secreting high-amount of VEGFA. The VEGFA promoter lacks Treg-specific transcription factor FOXP3 binding site. FOXP3 in association with locus-specific transcription factor STAT3 binds to VEGFA promoter to induce its transcription in Treg cells obtained from breast cancer patients. Treg cell-secreted VEGFA induces neo-angiogenesis from endothelial cells under in-vitro conditions. Targeting Tregs in mice with breast tumor reduces tumor growth as well as the level of neo-angiogenesis in the tumor tissue.

Regulatory lymphocytes: the dice that resolve the tumor endgame

A large number of cancer patients relapse after chemotherapeutic treatment. The immune system is capable of identifying and destroying cancer cells, so recent studies have highlighted the growing importance of using combinatorial chemotherapy and immunotherapy. However, many patients have innate or acquired resistance to immunotherapies. Long-term follow-up in a pooled meta-analysis exhibited long-term survival in approximately 20% of patients treated with immune checkpoint inhibitors or the adoptive transfer of chimeric T cells. It has been reported that high levels of immunoregulatory cells in cancer patients contribute to immunotherapy resistance via immunosuppression. Among the most important regulatory cell subtypes are the CD4+ T-regulatory cells (Tregs), identified by their expression of the well-characterized, lineage-specific transcription factor FOXP3. In addition to CD4+ Tregs, other regulatory cells present in the tumor microenvironment, namely CD8+ Tregs and IL10-producing B-regulatory cells (Bregs) that also modulate the immune response in solid and lymphoid tumors. These cells together have detrimental effects on tumor immune surveillance and anti-tumor immunity. Therefore, targeting these regulatory lymphocytes will be crucial in improving treatment outcomes for immunotherapy.

T-memory cells against cancer: Remembering the enemy.

BACKGROUND: Recently various types of immunotherapies have made immense progress in combating cancer. Adoptive cell therapy, being one of the most favorable forms of immunotherapy, is rapidly moving from bench to bed. MAIN BODY: Different types of T-memory cells are being used as promising candidates for adoptive cell therapy: T effector memory (TEM) cells which are terminally differentiated memory cells and attain effector function soon after re-stimulation; T central memory (TCM) cells which differentiate into effector T-memory subsets and T-effector cells after antigenic stimulation; and tissue T resident memory (TRM) cells which fight the tumor insult at the peripheral tissues. Recently, a new subtype of T-memory cells, T stem cell memory (TSCM) have been identified as the most favorable candidate for adoptive cell therapy as they exhibit higher persistence, anti-tumor immunity and self-renewal capacity in the tumor-bearing host. CONCLUSION: In this review, we briefly describe the concept and types of T-memory cells as well as their role as potential candidates for anti-cancer immunotherapy.